Cardiovascular complications and, in particular, acute cardiovascular events are most often life threatened medical conditions which require immediate action. However, these conditions can not always be unambiguously diagnosed. Specifically, some of the most common symptoms accompanying various types of heart diseases including acute cardiovascular events but also chronic heart dysfunctions such as chronic heart failure are symptoms which are characteristic for other (non-cardiovascular) diseases as well. Therefore, it is often difficult, cumbersome and time consuming to differentiate between a cardiovascular or other cause of an observed symptom. Said differentiation may also require the help of a specialist such as a cardiologist.
A typical symptom for cardiovascular complications, in particular, for an acute cardiovascular event or a more severe chronic heart failure is shortness of breath (dyspnea). As for other symptoms, dyspnea may have various causes including cardiovascular complications and non-cardiovascular pulmonary diseases.
In light of a potential cardiovascular cause of the symptom, it is highly advisable to properly diagnose its cause in a given patient, e.g., an emergency patient.
WO99/13337 discloses that surfactant proteins may be used as a biomarker for several specific pulmonary diseases including acute respiratory distress syndrome (ARDS).
In WO2004/077056 it is disclosed that systemic levels of surfactant proteins may be used as markers for heart failure. However, the disclosed techniques do not allow for a differential diagnosis of the cause of the elevated levels of the surfactant proteins. Specifically, it is known that pulmonary diseases or damages may also result in increased systemic levels of said proteins (Doyle 1997, Am J Respir Crit Care Med Vol. 156: 1217-1229). Accordingly, the disclosed methods shall inevitably produce false positive diagnostic results which in turn result in an inappropriate therapy (Svendstrup Nielsen, 2004, The European Journal of Heart Failure 6: 63-70).
Moreover, surfactant proteins have been described together with the N-terminal brain natriuretic peptide (NT-proBNP) to be indicative for the severity of heart failure according to the New York Heart Association (NYHA) classification (DePhasquale, 2004, Circulation 110:1091-1096).
NT-proBNP has been also described together with seven additional parameters as an indicator for acute heart failure in patients exhibiting dyspnea (Baggish 2005, American Heart Journal, 151:48-54).